(1) A periscope is used to see over the heads of a crowd. (4) Since the light rays coming from the object enter the eye of the person (or observer), it is possible to see the image of object through the periscope. The mirror M 2 then reflects the reflected rays of light towards the eye of the person looking into the periscope through the lower hole. (3) Mirror M 1 reflects these rays of light downwards, towards the second mirror M 2. (2) We look into the periscope from the bottom hole in front of lower mirror M 2. The light rays coming from the object fall on the plane mirror M 1. (1) The upper hole of periscope is turned towards the object to be seen so that the top mirror M 1, faces the object. (4) There are two holes in the periscope tube: one hole is in front of the top mirror M 1 and other hole is in front of the bottom mirror M 2. (3) Each plane mirror, however, makes an angle of 45° with the side of the tube. (2) The two plane mirrors are fitted in such a way that they are parallel to one another and their reflecting surfaces face each other. (1) A periscope consists of a long tube T having two plane mirrors M 1, and M 2 fitted at its two ends. The periscope makes use of two plane mirrors to see over the top of things.Ī periscope works on the reflection of light from two plane mirrors arranged parallel to one another. PeriscopeĪn optical instrument (or device) in which reflected light is periscope.Ī periscope is a long, tubular device through which a person can see objects that are out of the direct line of sight.īy using a periscope, we can see the objects on the other side of a high wall which cannot be seen by us directly. The reflected rays of the first plane mirror become incident rays for the second plane mirror. If the rays of light reflected by a plane mirror are incident on another plane mirror, then the reflected rays are reflected again. Our image in the plane mirror is laterally inverted (or sideways reversed). This means that the left side of our body becomes the right side in the mirror image whereas the right side of our body becomes left side in the mirror image. And if we lift our right hand, then our image in the plane mirror appears to lift its left hand. Change of sides of an object and its mirror image is called lateral inversion.įor example : If we stand in front of a plane mirror and lift our left hand, then our image in the plane mirror appears to lift its right hand. In an image formed by a plane mirror, the left side of object appears on the right side in the image whereas the right side of object appears on the left side in the image. (5) The image in a plane mirror is laterally inverted, we mean that the image in a plane mirror is sideways reversed with respect to the object. We will notice that our image in the plane mirror has head on the top and feet at the bottom just like us. (4) The image of an object in a plane mirror is erect, we mean that the image in plane mirror is the same side up as the object, the top of object is the top of image and bottom of object is the bottom image.įor example : If we look into a big plane mirror, we will see the image of our whole body. (3) The dimensions of image are exactly the same as that of the object. The image is neither enlarged (neither bigger than the object) nor diminished (nor smaller than the object).įor example : If a person is 1.75 metre tall, then his image in the plane mirror will also be exactly 1.75 metre tall. We mean that if a person is standing at a distance of 1 metre in front of a plane mirror, then his image will be formed at the same distance of 1 m behind the plane mirror. (2) The image in a plane mirror is the same distance behind the mirror as the object is in front of it. Our image seen in the plane mirror cannot be formed on a screen placed behind the plane mirror. Our image in the plane mirror is virtual (or unreal). It can be seen only by looking into the plane mirror.įor example : When we look into a plane mirror, we see the image of our face. (1) Image formed by a plane mirror is virtual, we mean that the image formed by a plane mirror cannot be obtained on a screen.
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